1. Field of the Invention
The present invention relates to a joint for fuel tank, which can be attached to, e.g., an opening of a resin fuel tank of a vehicle by means of welding, and relates to a method for manufacturing the same.
2. Description of the Related Art
A variety of piping structures, such as a feeder pipe connected to an oil filler, a fuel supply pipe connected to an engine, and a vapor exhaust pipe connected to a canister, are connected by means of welding to openings of a resin fuel tank of a vehicle, as joints.
Nowadays, fuel non-permeability of a fuel tank is sought. Such a fuel tank generally has a multilayer structure in which barrier resin layers being excellent in fuel non-permeability and high-density polyethylene layers are combined, with the outermost layer being formed from a high-density polyethylene, etc.
Meanwhile, since a main body of the joint is made of a polyamide or the like, the outermost layer of the fuel tank cannot be directly bonded to the joint main body by means of thermal welding. Therefore, a joint member having a junction—which can be welded to the periphery of an opening of a fuel tank and which can be molded integrally with the joint main body—is formed beforehand by means of insert molding or the like in advance. Subsequently, the fuel tank and the joint main body are integrated together via the junction by means of welding the junction to the fuel tank.
As an example of such a joint, JP-A-2000-8981 discloses that a case main body of a fuel shut-off valve is attached to a mounting hole of a fuel tank whose surface is made of polyethylene, via an annular welding section; a flange section of the case main body is made of a polyamide or polyacetal; and the annular welding section is made of a modified olefin resin to which a polar functional group is added.
U.S. Pat. No. 5,443,098 discloses a thermoplastic resin pipe joint for connecting a flexible fluid-conduit to a tank. A first elongated tubular member has a first end section for engaging with the conduit, and a second end section for engaging with a second member of the joint. The second member is attached to the tank. The first member of the joint is made of a polyamide for reinforcement. The second member of the joint is made of a resin, which is not for reinforcement purpose.